From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id DD3FAC433DB for ; Wed, 23 Dec 2020 06:33:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9BEE620759 for ; Wed, 23 Dec 2020 06:33:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727353AbgLWGdA (ORCPT ); Wed, 23 Dec 2020 01:33:00 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46528 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726282AbgLWGdA (ORCPT ); Wed, 23 Dec 2020 01:33:00 -0500 Received: from mail-ej1-x62f.google.com (mail-ej1-x62f.google.com [IPv6:2a00:1450:4864:20::62f]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AFFF0C061793 for ; Tue, 22 Dec 2020 22:32:19 -0800 (PST) Received: by mail-ej1-x62f.google.com with SMTP id lt17so21398847ejb.3 for ; Tue, 22 Dec 2020 22:32:19 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bytedance-com.20150623.gappssmtp.com; s=20150623; h=mime-version:from:date:message-id:subject:to:cc; bh=gLShtXRFUgewbIKfHtzkzQ5g7IaXVf3xlFIgWLLVqz8=; b=YpZMAt7xFq/77g6dwxVdwTalDKzaGm9/4PzOMbWOsWfDSVV9yzvU5yFAhxJVu7TgWM 06ta5T89UkCXgxA6Y3lY1nMBr9KNGsXBMVvTSyEM41CLdF4F9iDdv11RQDTp0U5cTenE QkHVsn+pXE3uBzQan4UEOxCVtUwC/LuLU/cAO/m44GzvDxnq/aeb99qr5AV35qmzE8jN 46YAhWhWp0XSzpfvt3rO1iB2xWB4B8csLwcLdSjdFOxySbFlwHL2G+I560sKxsGG1jfb 6WwdcVMj+dRLWvIJafAo/elklLL67cvrfdxsq4FrX/Mti9wKuhlbyWHcMnQV343nnSVF UvMA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:from:date:message-id:subject:to:cc; bh=gLShtXRFUgewbIKfHtzkzQ5g7IaXVf3xlFIgWLLVqz8=; b=YJH1vG5ukee1hi60wPN986xlqjqqu6srpkFmWAwqUrJoA88Qc1N8EUT0g8GD85d0pS TnAOaanjCmt5O6Iu4kdk4jVZq0O/2T9aZQnsiJ6+6OWnT4Z8iiHCLTMMYPS2tWt9Hz8r uHYYlnIESlHKm7B8UL3m/g4iW6bRWLoPtjcPVOTgvga2sumFl0RDS7RhdwzZHXlcKF+N 46aFphLdqduFLaFu4WQ1v9BlQI/S4aPA9JtOheOZpCB//PshmN8q/BQIW4Mx9iuZTy1q 8Y9EWZjs+57T1sYf9UKdF07t6fnUSK5qqmr24MX6kvDfhv6h9g/WXs0JF0RC8u1LWhm1 NJ2w== X-Gm-Message-State: AOAM532KqfXA6j8BryPSa0Vy4/PcGgGLX5AANwZ5bXQljCa7mJRa+8X7 kk1QpbhsxXHdPBagqukBaW9n7Qlj7EpEYSZeUJw2 X-Google-Smtp-Source: ABdhPJxs6lIntTC3Viz+5acTB3IEA1HMKnEybJJ/XyF/jDwD0HipwjDi0OgXmfi0YFe4Ee6AtCr/GLgvQ3xVMVqdmkM= X-Received: by 2002:a17:906:d0c2:: with SMTP id bq2mr22682863ejb.1.1608705138457; Tue, 22 Dec 2020 22:32:18 -0800 (PST) MIME-Version: 1.0 From: Yongji Xie Date: Wed, 23 Dec 2020 14:32:07 +0800 Message-ID: Subject: Re: [RFC v2 01/13] mm: export zap_page_range() for driver use To: Christoph Hellwig Cc: "Michael S. Tsirkin" , Jason Wang , Stefan Hajnoczi , sgarzare@redhat.com, Parav Pandit , akpm@linux-foundation.org, Randy Dunlap , Matthew Wilcox , viro@zeniv.linux.org.uk, axboe@kernel.dk, bcrl@kvack.org, corbet@lwn.net, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, kvm@vger.kernel.org, linux-aio@kvack.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Tue, Dec 22, 2020 at 11:44 PM Christoph Hellwig wrote: > > On Tue, Dec 22, 2020 at 10:52:09PM +0800, Xie Yongji wrote: > > Export zap_page_range() for use in VDUSE. > > Err, no. This has absolutely no business being used by drivers. Now I want to map/unmap some pages in an userland vma dynamically. The vm_insert_page() is being used for mapping. In the unmapping case, it looks like the zap_page_range() does what I want. So I export it. Otherwise, we need some ways to notify userspace to trigger it with madvise(MADV_DONTNEED), which might not be able to meet all our needs. For example, unmapping some pages in a memory shrinker function. So I'd like to know what's the limitation to use zap_page_range() in a module. And if we can't use it in a module, is there any acceptable way to achieve that? Thanks. Yongji